The invention relates to a rotary machine for glazing and decorating ceramic tiles, and a process therefor.
At present either the silk-screening method or the flexographic method are used for decoratively glazing ceramic tiles.
The silk-screening method, using either a flat or a rotary cylindrical screen, presents numerous drawbacks. For example, half-tones are difficult to obtain, and due to the structure of the screens, whether flat or cylindrical, it is not possible to print the decoration on the edges of the tiles, where the upper surface meets the side surfaces. This latter defect is particularly evident in the prior art, where good reproduction of a decorative pattern can only be perfect away from the edges, where good contact with the tile is guaranteed.
A further drawback of the above method is the need to have an operative continually at the workplace, to control the machine efficiency and to clean the screens themselves.
Further drawbacks are the limited lifespan of the screens and the impossibility of having continuous printing screens.
The flexographic method also suffers from some of the above drawbacks, as well as presenting some inconveniences of its own: for example, it is impossible to print using only very small quantities of glaze, and too frequently the printing process actually leads to tile breakage, especially of still-unfired tiles.